Apparatus for thickening liquid slurry stock



Aprifi 110, @951 J. BAXTER, JR 2548,43?

APPARATUS FOR THICKEN LNG LIQUID SLURRY STOCK Filed D80. 24, 1948 I Sheets-Sheet 1 ATTO RN EYS April 10, 1951 J. BAXTER, JR

APPARATUS FOR THICKENING LIQUID SLURRY STOCK 2 Sheets-Sheet 2 Filed Dec. 24, 1948 ATTORNEYS Patented Apr. 10, 1951 APPARATUS FOR THICKENING LIQUID SLURRY STOCK Joseph Baxter, Jr., Franklin, Ohio, assignor to The Black-Clawson Company, Hamilton, Ohio,

acorporation of Ohio Application December 24, 1948, Serial No. 67,173 I This invention relates to apparatus for the removal of water or other liquids from liquid slurry stock such as paper making stock, industrial wastes and the like. 7

One of the principal objects of the invention is to provide centrifugal apparatus for removing liquid from stock which is of simple, lightweight and compact construction, which continuously unloads the thickened stock from which the liquid has been removed, and which has high operating capacity with relatively low power requirements for economical operation.

It is also an object of the invention to provide centrifugal apparatus for removing liquid from liquid slurry stock wherein the percentage of liquid removed from the stock, and hence the consistency of the thickened stock, may be readily predetermined and controlled by simple regulation of the speed of rotation of the driven unit therein.

Another object is to provide such centrifugal liquid-removing apparatus wherein'a rotating frusto-conical perforate screen member is arranged to receive stock for thickening at the smaller end thereof for travel upwardly therein and to discharge the liquid therefrom outwardly through the perforations therein, and wherein the thickened material is discharged inwardly from the upper end of the screen member into a stationary funnel member for gravity flow from the apparatus.

An additional object is to provide such apparatus wherein the rotating screen member includes an inwardly turned discharge lip overhanging the discharge funnel to provide a trough for temporarily retaining the thickened stock and temporarily retarding the discharge thereof in accordance with the speed of rotation of the screen member to control the final consistency of the resulting thickened stock.

A further object is to provide such centrifugal apparatus which has relatively few moving parts and bearing points for easy operation with minimum wear, which is effectively self-cleaning and which also is constructed for quick disassembly to facilitate maintenance thereof.

Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings- Fig. l is a perspective view showing centrifugal liquid-removing apparatus in accordance with the invention;

Fig. 2 i a perspective view of the apparatus 12 Claims. (Cl. 21063) with the cover removed and a portion at the front broken away to show the internal construction and arrangement;

Fig. 3 is a vertical section through the apparatus of Fig. 1;

Fig. 4 is a detail view in perspective showing the member which forms the lower end of the rotating screen unit of'the apparatus;

Fig. 5 is an exploded fragmentary View in perspective showing the lower end of the discharge funnel and the supporting collar therefor;

Fig. 6 is an enlarged sectional view showing a fragment of the perforate screen member;

Fig. 7 is a fragmentary plan view of the top of the discharge funnel showing one of the plows for aiding discharge of thickened stock from the screen into the funnel; and

Fig. 8 is a diagrammatic view in vertical section illustrating the operation of the apparatus.

The present invention haspa-rticular relation to apparatus for thickening or condensing liquid slurry stock by mechanical removal of water or other liquid therefrom, there being many occasions for such liquid-removing operations in many branches of industry. As one example, great quantities of water are used in the paper industry as a vehicle for transporting the fibers used in paper manufacture from one stage of the paper making process to another, and some of these process steps commonly require dilution to consistencies as low as 0.5 followed by other process steps requiring substantially higher consistencies, for example from 4 to 10%. Thus in a mill operating at a production capacity of tons of paper per 24 hours, the how of stock at 0.5% consistency would be at a rate of 3300 gallons per minute as compared with 425 gallons per minute at 4%. It will be readily apparent that in order to fulfill these operating conditions, enormous quantities of water must be removed quickly and economically from the'stock and without removing any substantial amount ofthe usable fiber with the water, this Water ordinarily being returned to the system at another point, for example for initial dilution of the stock.

Another field in which quick and effective removal of large quantities of liquid from liquid slurry stocks is desirable is in the treatment of industrial wastes from mills and factories to prevent stream pollution. The waste Water from many types of mills includes suspended solids which it is desirable to preventfrom reaching the streams into which these mills discharge, either because they tend to pollute the streams or be-.

cause they are of substantial value if they can be recovered economically from the waste water. For example, packing houses and other plants handling meat and meat products, tanneries, mills handling metal products, and many other types of industries have appreciable percentages of solids in their waste water which should be removed before the water is finally discharged to promote economical operation and adequate prevention of stream pollution.

The present invention provides a simple and compact centrifugal apparatus for quickly and easily thickening liquid slurry stocks by separation of water therefrom, and this apparatus is well suited for use in thickening paper stock as well as for other liquid-removing operations. Referring to the drawings, which illustrate a preferred embodiment of the present invention, the lower part lb of the casing forms an inlet chamber I I for the stock to be thickened, which enters through an inlet passage I2. The upper wall of easing member ID is provided with an opening I3 from which a cylindrical collar l4 extends upw'ardly into a chamber I5 formed by an annular upper part It of the casing mounted on the lower casing member Ill. The casing member IE is relieved at the front of the machine to form an outlet IT from chamber I5 into a trough l8 formed between the front wall of the casing and the member ID, gravity drainage being provided from trough 18 to a suitable pipe or other receptacle as indicated by arrow 22.

.A generally frusto-conical screen unit is mounted for rotation within the outer chamber I5 with the smaller end thereof lowermost and extending through the opening I3 into the inlet chamber II to receive therefrom the stock to be thickened. The screen unit 25 includes a frustoconical main section formed of perforate material having perforations of suitable size to prevent the passage of the suspended solids in a given stock to be thickened, and for use with paper making stock, the screen section 30 is preferably formed of a perforate rubber sheet material sold under the trade name Multipore rubber. This material is obtainable commercially in sheets of sufiicient thickness and rigidity to hold a desired shape, and it has multiple minute perforations extending therethrough substantial- 1y perpendicularly to the surfaces of the sheet. It is understood to be produced by successively flowing a film of latex on to a supporting layer of cloth and then subjecting the cloth to a blast of air from below to blow out holes in the film through the spaces between adjacent threads in the cloth, these steps being repeated until a sheet of desired thickness is formed. The supporting cloth is removed from the finished sheet to leave a pattern of holes therein corresponding directly to the pattern of the mesh in the cloth, and such sheets are available commercially in different grades having respectively 1100, 3200 and 6400 perforations per square inch, the perforations ranging from 0.004 to 0.014 inch in diameter.

This perforate rubber sheet has several advantageous features when used with paper making stock. Its inherent slipperiness when wet facilitates sliding travel of thickened stock along its surface, and this effect is further aided by the smoothness of its surface as compared, for example; with the surface of wire mesh or of sheet metal in which holes have been punched. Moreover, since the holes in the sheet are of such exceedingly small dimensions, there is minimum tendency for useful paper fibers to be trapped therein orto pass therethrough. In addition,

since the holes are of substantially uniform and approximately cylindrical configuration when the sheet is flat, they assume a generally frustoconical shape when the sheet is formed into a cylinder or cone, as shown at 3| in Fig. 6, and since the larger end of each of these holes is at the outer surface of the cone, any fiber or other particle sumciently small to enter the smaller, inner end of one of these holes will readily pass therethrough without clogging.

The perforate section 39 of the screen unit 25 is suspended from a supporting ring 33, which is mounted for rotation with respect to the upper casing member l6 by a plurality of bearing units 35 secured to the inwardly tapered upper end portion 36 of casing part I 6, there being three of these bearing units disposed around the circumference of the casing part 36 at substantially from each other. For minimum vibration and noise in operation, each'of the bearing units 35 may advantageously comprise a wheel having a tapered rubber tire 3'5 and journaled in a suitable bearing such as a ball or roller bearing secured to the casing portion 36, and the supporting ring 33 is formed with a tapered surface portion 38 arranged to ride on tires 31. The supporting ring 33 also includes a V-belt sheave portion 40 which receives a V-belt 4i driven by pulley 42, which is in turn driven by motor 44 through a variable speed transmission unit 45.

The upper end of the screen section 30 is clamped between the inner surface of supporting ring 33 and a downwardly extending frusto-conical portion 49 of a curved lip member 50, which includes an outwardly projecting flange portion 5| bolted to ring 33 at 52. The lip member 58 extends inwardly from the upper periphery of the screen and is curved in such manner as to form an inverted trough 55 surrounding the upper end of the screen. The lower end of screen section 30 is similarly clamped between a pair of inner and outer frusto-conical members 60 and GI which extend into the collar I4 and opening I3 from inlet chamber I I. The part 69 is provided with clamp bosses 62 (Fig. 4) to receive the right angled clamp bolts 63 which extend outwardly below the part BI, and the part BI is provided with upper and lower flanges 65 and 66 which extend outwardly therefrom to serve as flinger rings or deflectors for preventing the stock from traveling up the outer surface of the screen unit from chamber II.

A stationary cone or funnel member II! is mounted within the screen unit 25 to receive the thickened stock therefrom. It includes a discharge pipe II which extends at its lower end through the bottom wall of the casing member Ill and is received within a supporting socket l2 bolted to casing member ID. As shown in Fig. 5, the lower end of pipe 11 is turned to a slight taper and is provided with a plurality of welded keys I3 for engagement in receiving slots 14 in the tapered inner surface 15 of socket member i2, thus supporting the funnel II! in upright position and preventing rotation thereof with respect to the casing. To facilitate disassembly of the apparatus, the inner surface of funnel member 10 is shown as provided with a pair of orange peel sections I6 arranged with their pointed ends uppermost to serve as lift lugs to receive lifting hooks for hoisting the funnel member out of the machine when desired. A plurality of spiral plows I7 may be secured along the upper rim of funnel member ID to facilitate discharge of the thickened stock into the funnel member during operation of the device, the plows 'I'I being arranged with their outer ends pointed opposite to the direction of rotation of the screen unit 25.

In order to conceal the working parts of the apparatus and give a finished appearance thereto, there is provided a top cover 86 of generally pear-shaped configuration having a center aperture 81 to provide for visual observation of the interior of the apparatus, and this cover is readily removable when desired. A plurality of supporting pins 82 are secured to the casing part 16 by means of bracket members 83, and these pins are received in socket members 84 welded within the downwardly extending flange portion of the cover. The cover 80 is supported for swinging movement to a position exposing the screen by means of a rod 85 Welded or otherwise secured to the under surface thereof and received within a tube 85 extending upwardly from the upper surface of casing part It. The rod 85 is sufiicient length to have a portion-thereof remain within tube 85 when the cover 8!} has been lifted sufficiently to effect disengagement of the pins 82 and sockets 84. In order to guide the cover into proper position for reengagement of these pins and sockets, a fin or key 81 is secured to the upper end of rod 85 and is arranged to be received in.

level thereof in chamber I! above the lower end F of the screen unit but below the upper end of collar [4, in order to prevent the stock from short circuiting the screen and passing directly to the outlet chamber i5 and discharge trough it. As. the frusto-conical screen rotates, frictional contact between its inner surface and the stock will cause the stock to travel up along the inner surface of the screen, due to the centrifugal force which isv thus generated, and since the lower end portion of the screen unit formed by the conical member 69- is imperforate, the stock will accelerate in its upward travel until it reaches the perforate screen section 3!). At this point, free discharge of water will begin, the water being discharged outwardly through the perforations 3] into the outlet chamber 15, whence it flows to the discharge trough H8.

The stock accordingly begins to thicken as soon as it reaches the perforate screen section 33, and the thickened material continues to advance up the inner surface of the screen following a more or less spiral path, while the lower end of the spinning screen continues to pick up fresh stock. As this action continues, the effective centrifugal force-will increase as the stock moves further away from the axis of the screen, and also the fibers will be-spread over a continually increasing area as they approach the upper end of the perforate screen section. As a result, discharge of the residual free water is facilitated, since the fibers are drawn increasingly apart and form a mat of constantly decreasing thickness which presents less resistance to the passage of the water therethrough than would be the case if the same fiber content were spread over a lesser area.

When the thickened stock reaches the upper end of the perforate screen section it continues to travel upwardly along the flange 49 and into the trough 55, the lower end of flange 49 being beveled at hi! to facilitate this action. Since further upward travel of the stock is then prevented by the overhanging portion of lip 50, the stock collecting in trough 55 is caused to level off to form a layer having a substantially cylindrical inner surface as indicated at in Fig. 8. With the stationary funnel member l9 arranged as shown with its upper rim extending outwardly and upwardly into the trough 55, the stock will accumulate in the trough until a balance column is forced inwardly above the rim of the funnel, and this stock is free to fall by gravity downwardly into the funnel and its discharge pipe ll. The plows l1 mounted as shown along the upper rim of the funnel facilitate this discharge by deflecting the accumulated stock inwardly over the rim of the funnel.

It will accordingly be seen that this apparatus is capable of continuous operation to reduce the water content of the stock supplied to its inlet passage 52, with the water being continuously removed by way of trough IS and the thickened stock similarly continuously discharged inwardly and downwardly through the funnel 1G and pipe H. In addition, the percentage of water removed, and hence the consistency of the thickened stock as discharged from pipe H, may be readily controlled to a predetermined range by simple regulation of the speed of rotation of the screen unit 25. This result is due to two main factors. In the first place, increase in the speed of rotation of the screen will produce a corresponding increase in the centrifugal force effective on the stock as it travels up the inner surface of the perforate screen section. In addition, the centrifugal force effective on the stock accumulating in trough 55 will similarly increase, thus retarding the inward discharge of the thickened stock to funnel 7i! and causing this accumulated stock to act as a dam retarding upward travel of the stock from the perforate section of the screen, with resulting increased drainage therefrom.

This apparatus is accordingly simple to operate as well as easy to maintain. Since the control of the apparatus is centered in the adjustment of the variable ratio transmission, even an inexperienced operator can readily understand it.

Furthermore, samples of the thickened stock can be readily obtained through the opening in the top cover if desired, and the results of adjustment can thus be quickly observed. The simplicity of the moving parts of the application minimizes the possibility of breakdown in operation, and also if it is desired to disassemble the apparatus for any purpose, this can be quickly and easily done as described. Still another advantage of the invention is the relatively small size and compact arrangement of the apparatus, which minimizes the floor space required in a mill, and also its streamlined construction contributes both to its appearance and to the ease with which the apparatus can be kept clean and in good running order.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. Apparatus of the character described for thickening a liquid slurry stock by removing liquid therefrom comprising a frusto conical perforate screen member mounted with the larger end thereof uppermost, means for supplying stock to be thickened to the lower end of said screen member, means for rotating said screen member to cause said stock to travel upwardly along the inner surface thereof with accompanying discharge of liquid outwardly through the perforations therein, imperforate collecting means defining a chamber for receiving the thickened stock from said screen member, means mounting said collecting means in stationary position inwardly of the perforate surface of said screen member, and means forming a peripheral discharge lip extending inwardly from the upper end of said screen member, said lip being curved radially inwardly of said screen member and downwardly to a position located radially inwardly of the periphery of said collecting means to form an inverted trough partially overhanging said chamber for guiding said thickened stock from said screen member into said chamber.

2. Apparatus of the character described for thickening a liquid slurry stock by removing liquid therefrom comprising a frusto-conical perforate screen member mounted with the larger end thereof uppermost, means for supplying stock to be thickened to the lower end of said screen member, means for rotating said screen member to cause said stock to travel upwardly along the inner surface thereof with accompanying discharge of liquid outwardly through the perforations therein, imperforate collecting means defining a chamber for receiving the thickened stock from said screen member, means mounting said collecting means in stationary position inwardly of the perforate surface of said screen member, means forming a peripheral discharge lip extending inwardly from the upper end of said screen member, said lip being curved radially inwardly of said screen member and downwardly to a position located radially inwardly of the periphery of said collecting means to form an inverted trough partially overhanging said chamber for guiding said thickened stock from said screen member into said chamber, and means forming a discharge outlet extending downwardly from said chamber for continuous gravity discharge of said thickened stock therefrom.

3. Apparatus of the character described for thickening a liquid slurry stock by removing liquid therefrom comprising a frusto-conical perforate screen member mounted with the larger end thereof uppermost, means for supplying stock to be thickened to the lower end of said screen member, means for rotating said screen member to cause said stock to travel upwardly along the inner surface thereof with accompanying discharge of liquid outwardly through the perforations therein, imperforate collecting means defining a chamber for receiving the thickened stock from said screen member, means mounting said collecting means in stationary position inwardly of the perforate surface of said screen member, means forming a peripheral discharge lip extending inwardly from the upper end of said screen member, said lip being curved through approximately 180 and having the inner periphery thereof located radially inwardly of and below the upper end of said collecting means to effect positive guiding of said thickened stock from said screenmember into said chamber.

4. Apparatus of the character described for thickening a liquid slurry stock by removing liquid therefrom comprising a frusto-conical perforate screen member mounted with the smaller end thereof lowermost, means forming a peripheral lip extending inwardly from the upper end of said screen member to provide an inverted trough, means for supplying stock to be thickened to the lower end of said screen member, means for rotating said screen member to cause said stock to travel upwardly along the inner surface thereof into said trough with accompanying discharge of liquid from said stock outwardly through the perforations in said screen member, a generally frusto-conical imperforate stationary member mounted Within said screen member with the larger end thereof uppermost and arranged to extend upwardly and outwardly into said trough to receive the thickened stock inwardly and downwardly therefrom, said lip extending inwardly and downwardly from said screen member to a position located radially inwardly of and below the upper end of said stationary member to guide said thickened stock into said stationary member, and said lip forming means including an imperforate flange portion extending downwardly within said screen member from said trough to a position located below and approximately in vertical alignment with the outer periphery of said stationary member to prevent discharge of liquid from said stock after said stock reaches a distance from the axis of said screen member approximately equal to the maximum radius of said stationary member.

5. Apparatus of the character described for thickening a liquid slurry stock by removing liquid therefrom comprising a casing including means forming an inlet chamber for receiving said stock to be thickened and an outlet chamber for the liquid removed from said stock, a frusto-conical perforate screen member, means mounting said screen member for rotation within said casing with the smaller end thereof lowermost and extending within said inlet chamber to receive stock therefrom, means forming a peripheral lip extending inwardly from the upper end of said screen member to provide an inverted trough along the upper end of said screen member, means for rotating said screen member to cause said stock to travel upwardly along the inner surface thereof to said trough with accompanying discharge of liquid therefrom outwardly through the perforations in said screen member, a generally frusto-conical imperforate stationary member mounted within said screen member with the larger end thereof uppermost and arranged to extend upwardly and outwardly into said trough to receive the thickened stock inwardly and downwardly therefrom, said lip being curved radially inwardly of said screen member and downwardly to a position located radially inwardly of and below the upper periphery of said stationary member to guide said thickened stock from said screen member into said stationary member, and means for regulating the speed of rotation of said screen member to vary the consistency of said thickened stock discharged into said stationary member.

6. Apparatus of the character described for thickening a liquid slurry stock by removing liquid therefrom comprising a casing including means forming an inlet chamber for receiving said stock to be thickened and an outlet chamber for the liquid removed from said stock, a frusto-conical perforate screen member, means mounting said screen member for rotation within said casing with the smaller end thereof member, and an imperforate funnel member mounted within said screen member with the larger end thereof uppermost and arranged to extend upwardly and outwardly into said trough to receive the thickened stock inwardly and downwardly therefrom, said lip, being curved radially inwardly of said screen member and downwardly to a position located radially inwardly of and below the upper periphery of said stationary member to guide said thickened stock from said screen member into said stationary member, the lower end of said funnel member extending through said inlet chamber for gravity discharge of said thickened stock.

7. Apparatus of the character described for thickening a liquid slurry stock by removing liquid therefrom comprising a casing forming an inlet chamber for stock to be thickened, said casing having an opening in the upper wall thereof, a frusto-conical screen unit open at both ends thereof and including an imperforate section at the smaller end thereof and a perforate section adjacent said imperforate section, means mounting said screen unit for rotation above said casing with said smaller end thereof lowermost and with said imperforate end arranged to extend into said inlet chamber through said opening to receive stock therefrom, means for rotating said screen unit to cause said stock to travel upwardly from said inlet chamber along the inner surface of saidscreen unit and to effect centrifugal discharge of liquid therefrom through said perforate screen section above said casing while the resulting thickened stock continues to travel upwardly within said screen, an imperferate inverted trough member secured within the upper end of said screen unit to receive said thickened stock from said perforate screen section for discharge radiallyinwardly of said'screen unit and downwardly, and an imperforate container supported within said screen unit with the upper periphery thereof located within said trough member to receive said stock discharged from said trough member.

8. Apparatus of the character described for thickening a liquid slurry stock by removing liquid therefrom comprising a casing forming an inlet chamber for stock to be thickened, means forming an outlet chamber above said inlet chamber, said casing having an opening in the upper wall thereof connecting said chambers, a collar extending upwardly from said upper casing wall and surrounding said opening to prevent backilow from said outlet chamber, a frustoconical screen unit including an imperforate small end section and a perforate section adjacent said i'znperforate section, means mounting said screen unit for rotation with said perforate section located above said collar and with said imperferate section arranged to extend through said opening into said inlet chamber to rezeive stock therefrom, means for rotating said screen unit to cause said stock to travel upwardly from said inlet chamber along the inner surface of said imperforate screen section and to effect centrifugal discharge of liquid from said stock through said perforate screen section into said outlet chamber while the resulting thickened stock continues to travel upwardly within said screen unit, said screen unit having an outwardly projecting flange thereon adjacent the lower end of said perforate section and above said collar to prevent flow of liquid from said outlet chamher through said opening to said inlet chamber, and means for effecting continuous controlled discharge of said thickened stock from the upper end of said screen unit.

9. Apparatus oi the character described for thickening a liquid slurry stock by removing liquid therefrom comprising a casing forming an inlet chamber for stock to be thickened, means forming an outlet chamber above said inlet chamher, said casing having an opening in the upper wall thereof connecting said chambers, a collar extending upwardly frcm said upper casing wall and surrounding said opening to prevent backflow from said outlet chamber, .a frusto-conical screen unit including an imperforate small end section and a perforate section adjacent said imperforate section, means mounting said screen unit for rotation with said perforate section lo- ,cated above said collar and with said imperferate section arranged to extend through said opening into said inlet chamber to receive stock therefrom, means for rotating said screen unit to cause said stock to travel upwardly from said inlet chamber along the inner surface of said imperforate screen section and to efiect centrifugal discharge of liquid from said stock through said perforate screen section into said outlet chamber while the resulting thickened stock continues to travel upwardly within said screen unit, said screen unit including an imperforate portion extending inwardly fromthe upper end thereof to form an inverted trough for receiving said thickened stock, and a stationary imperforate funnel m'mber mounted within said screen unit with the upper end thereof extending upwardly and outwardly into said trough to receive said thickened stock therefrom and including a discharge pipe extending downwardly through said lower casing for continuous gravity discharge of said thickened stock, said upper imperforate portion of said screen unit extending from a position within said screen unit located below and approximately in vertical alignment with the upper periphery of said funnel to a position located radially inwardly of and below said upper periphery of said funnel to guide said thickened stock from said screen unit into said funnel while preventing discharge of liquid therefrom after said stock reaches a distance from the axis of said screen unit approximately equal to the maximum radius of said funnel.

10. Apparatus of the character described for thickening a liquid slurry stock by removing liquid therefrom comprising a frusto-conical perforate screen member mounted with the smaller end thereof lowermost, means forming a peripheral lip extending inwardly from the upper end of said screen member to provide an inverted trough, means for supplying stock to be thickened to the lower end of said screen memher, means for rotating said screen member to cause said stock to travel upwardly along the inner surface of said screen member into said trough with accompanying discharge of liquid from said stock outwardly through the perforations in said screen member, a generally frustoconical imperforate stationary member mounted 11 within said screen member with the larger end thereof uppermost and arranged to extend upwardly and outwardly into said trough and means mounted along the upper rim of said stationary member for deflecting the thickened stock inwardly and downwardly from said trough into said stationary member.

11. Apparatus of the character described for thickening a liquid slurry stock by removing liquid therefrom comprising a frusto-conical 1 screen member including a perforate section formed of rubber sheet material having multiple minute perforations extending therethrough, means mounting said screen member for rotation with the smaller end thereof lowermost; means for supplying stock to be thickened to said small end of said screen member, means for rotating said screen member to cause said stock to travel upwardly along the inner surface of said rubber section and to effect centrifugal discharge of liquid from said stock through said perforations, imperforate means defining a stationary chamber within said screen member for receiving the thickened stock therefrom, and means forming a peripheral discharge lip extending inwardly from the upper end of said screen member into overhanging relation with said stationary means, said lip being curved radially inwardly of said screen member and downwardly to a position located radially inwardly of the periphery of said chamber means to form an inverted trough partially overhanging said chamber for guiding said thickened stock from said screen member into said stationary chamber.

12. Apparatus of the character described for thickening a liquid slurry stock by removing liquid therefrom comprising a casing forming an inlet chamber for stock to be thickened, means forming an outlet chamber above said inlet chamber, said casing having an opening in the upper wall thereof connecting said chambers, a collar extending upwardly from said upper casing wall and surrounding said opening to prevent backflow from said outlet chamber, a frustoconical screen unit including an imperforate small end section and a perforate section adjacent said imperforate section and formed of rubber sheet material having multiple minute perforations extending therethrough, means mounting said screen unit for rotation with said perforate section located above said collar and with said imperforate section arranged to extend through said opening into said inlet chamber to receive stock therefrom, means for rotating said screen unit to cause said stock to travel up wardly from said inlet chamber along the inner surface of said imperforate screen section and to effect centrifugal discharge of liquid from said stock through said perforate screen section into said outlet chamber while the resulting thickened stock continues to travel upwardly within said screen unit, said screen unit including an imperforate portion extending inwardly from the upper end thereof to form an inverted trough for receiving said thickened stock, and a stationary imperforate funnel member mounted Within said screen unit with the upper end thereof extending upwardly and outwardly into said trough to receive said thickened stock therefrom and including a discharge pipe extending downwardly through said lower casing for continuous gravity discharge of said thickened stock, said upper imperforate portion of said screen unit extending from a position within said screen unit located below and approximately in vertical alignment with the upper periphery of said funnel to guide said thickened stock from said screen unit into said funnel while preventing discharge of liquid therefrom after said stock reaches a distance from the axis of said screen unit approximately equal to the maximum radius of said funnel.

JOSEPH BAX'I'ER, JR.

REFERENCES CITED The following references are of record in the 

1. APPARATUS OF THE CHARACTER DESCRIBED FOR THICKENING A LIQUID SLURRY STOCK BY REMOVING LIQUID THEREFROM COMPRISING A FRUSTO-CONICAL PERFORATE SCREEN MEMBER MOUNTED WITH THE LARGER END THEREOF UPPERMOST, MEANS FOR SUPPLYING STOCK TO BE THICKENED TO THE LOWER END OF SAID SCREEN MEMBER, MEANS FOR ROTATING SAID SCREEN MEMBER TO CAUSE SAID STOCK TO TRAVEL UPWARDLY ALONG THE INNER SURFACE THEREOF WITH ACCOMPANYING DISCHARGE OF LIQUID OUTWARDLY THROUGH THE PERFORATIONS THEREIN, IMPERFORATE COLLECTING MEANS DEFINING A CHAMBER FOR RECEIVING THE THICKENED STOCK FROM SAID SCREEN MEMBER, MEANS MOUNTING SAID COLLECTING MEANS IN STATIONARY POSITION INWARDLY OF THE PERFORATE SURFACE OF SAID SCREEN MEMBER, AND MEANS FORMING A PERIPHERAL DISCHARGE LIP EXTENDING INWARDLY FROM THE UPPER END OF SAID SCREEN MEMBER, SAID LIP BEING CURVED RADIALLY INWARDLY OF SAID SCREEN MEMBER AND DOWNWARDLY TO A POSITION LOCATED RADIALLY INWARDLY OF THE PERIPHERY OF SAID COLLECTING MEANS TO FORM AN INVERTED TROUGH PARTIALLY OVERHANGING SAID CHAMBER FOR GUIDING SAID THICKENED STOCK FROM SAID SCREEN MEMBER INTO SAID CHAMBER. 